JP7313026B2 - Residual chlorine meter and residual chlorine concentration measurement method - Google Patents

Description

The present invention relates to a residual chlorine meter and a residual chlorine concentration measuring method for measuring the residual chlorine concentration of test liquids such as tap water.

A galvanic residual chlorine meter is known as a reagentless residual chlorine meter. In the galvanic residual chlorine meter, a platinum electrode or a gold electrode is used as a working electrode, and a silver/silver chloride electrode is used as a reference electrode. The measurement principle of the galvanic residual chlorine meter is generally as follows. That is, when the working electrode and the reference electrode are immersed in the test solution, a current flows between the electrodes due to oxidation-reduction reaction, and a potential difference is generated between the electrodes. The potential difference between the electrodes varies depending on the residual chlorine concentration of the test liquid. Therefore, the residual chlorine concentration of the sample liquid can be measured based on the potential difference (voltage) between the electrodes.

A polarographic residual chlorine meter is known as another type of residual chlorine meter that does not require a reagent. Similar to the galvanic residual chlorine meter, most polarographic residual chlorine meters use a platinum electrode or a gold electrode as the working electrode and a silver/silver chloride electrode as the counter electrode. However, in the polarographic residual chlorine meter, unlike the galvanic residual chlorine meter, a voltage is applied between the electrodes, and in this state, the residual chlorine concentration of the test solution is measured based on the current value between the electrodes. The measurement principle of the polarographic residual chlorine meter is generally as follows. That is, a working electrode and a counter electrode are immersed in a test solution, and a voltage is applied between the electrodes. As the applied voltage is increased in the negative direction, the reduction reaction proceeds and the current flowing between the electrodes increases. However, if the applied voltage is further increased in the negative direction, a phenomenon occurs in which the current flowing between the electrodes does not change even if the applied voltage is changed. As the applied voltage continues to increase in the negative direction, the current flowing between the electrodes begins to increase again. In a state in which the current flowing between the electrodes does not change even if the applied voltage is changed, the current value between the electrodes, which is determined according to the residual chlorine concentration of the test liquid, can be stably measured. Therefore, by applying an applied voltage having a voltage value that causes the above phenomenon between the electrodes and measuring the current value between the electrodes in this state, the residual chlorine concentration of the test liquid can be measured with high accuracy.

By the way, in both galvanic and polarographic residual chlorine meters, oxidation-reduction reaction products and the like adhere to the working electrode when the residual chlorine concentration is measured. If oxidation-reduction reaction products or the like adhere to the working electrode, the measurement accuracy of the residual chlorine concentration is lowered. The following method is known as a method for suppressing the decrease in measurement accuracy of the residual chlorine concentration.

That is, there is a known method of wiping off oxidation-reduction reaction products and the like adhering to the working electrode using a soft cloth, melamine sponge, or the like before measurement, mainly in portable galvanic residual chlorine meters.

Further, in a polarographic residual chlorine meter of the type that is mainly attached to water tanks, pipes, etc. of water purification plants, industrial water treatment facilities, etc., and continuously measures the residual chlorine concentration of a test solution, there is known a method in which polishing beads are housed in a container, a working electrode is arranged so as to face the container, and the working electrode is polished with the polishing beads by circularly moving the working electrode using a motor or the like or by pouring the test solution into the container (see Patent Document 1 below). .

JP 2015-117939 A

However, the above method has the following problems.

First, the method of wiping off oxidation-reduction reaction products and the like adhering to the working electrode with a melamine sponge or the like has the problem that the user has to wipe the working electrode before measurement, which is troublesome.

Next, regarding the method of polishing the working electrode with polishing beads, in order to realize this method, a large-scale device is required, such as a device for circularly moving the working electrode with a motor, or a device for introducing a test solution into a container containing polishing beads and causing the test solution to flow into the container.

The present invention has been made in view of the above-described problems, for example, and an object of the present invention is to provide a residual chlorine meter and a residual chlorine concentration measuring method that can suppress the decrease in the measurement accuracy of the residual chlorine concentration due to the adhesion of oxidation-reduction reaction products and the like to the working electrode without requiring trouble for the user and without increasing the size, complexity, or cost of the residual chlorine meter.

In order to solve the above problems, the residual chlorine meter of the present invention has a first electrode that is a working electrode and a second electrode that is a reference electrode or a counter electrode immersed in a test solution, a measurement part that measures the residual chlorine concentration of the test solution based on the voltage between the first electrode and the second electrode, a pretreatment part that applies a pretreatment voltage between the first electrode and the second electrode, and after applying the pretreatment voltage, the application of the pretreatment voltage is stopped, and then the residual chlorine concentration of the test solution. and a control unit that controls the measurement unit and the preprocessing unit so that the measurement is performed.

According to the residual chlorine meter of the present invention, by applying a pretreatment voltage between the first electrode and the second electrode, it is possible to remove at least part of the oxidation-reduction reaction products and the like attached to the first electrode due to the measurement of the residual chlorine concentration performed last time or earlier. Then, by measuring the residual chlorine concentration after finishing the application of the pretreatment voltage, it is possible to suppress the decrease in the measurement accuracy of the residual chlorine concentration due to the adhesion of oxidation-reduction reaction products and the like to the first electrode. Therefore, it is possible to eliminate the work of wiping off oxidation-reduction reaction products and the like adhering to the working electrode with a melamine sponge or the like before measurement. In addition, it is possible to eliminate the need for a large-scale device for polishing the working electrode with polishing beads.

In the residual chlorine meter of the present invention, the pretreatment section may sweep the pretreatment voltage. By sweeping the pretreatment voltage, it is possible to stabilize the measurement accuracy of the residual chlorine concentration of the test liquid as compared with the case of applying a DC pretreatment voltage.

Further, in the residual chlorine meter of the present invention, the pretreatment section may sweep the pretreatment voltage around 0 V so that the amplitude on the positive side and the amplitude on the negative side are equal to each other. With this configuration, it is possible to prevent the design of the electric circuit that constitutes the preprocessing section or the control section from becoming complicated.

Further, in the residual chlorine meter of the present invention, the pretreatment section may be configured to sweep the pretreatment voltage at a constant speed. Also with this configuration, it is possible to prevent the design of the electric circuit that constitutes the preprocessing section or the control section from becoming complicated.

Further, in the residual chlorine meter of the present invention, the control unit may determine whether or not the number of measurements of the residual chlorine concentration by the measurement unit after applying the pretreatment voltage is a predetermined number or more, and when the number of measurements is the predetermined number or more, apply the pretreatment voltage before the next measurement of the residual chlorine concentration by the measurement unit, and when the number of measurements is less than the predetermined number, control the pretreatment unit so that the pretreatment voltage is not applied before the next measurement of the residual chlorine concentration by the measurement unit. According to this configuration, the frequency of applying the pretreatment voltage can be reduced. Therefore, it is possible to speed up the measurement work and reduce the power consumption while suppressing the decrease in the measurement accuracy of the residual chlorine concentration caused by the oxidation-reduction reaction products and the like adhering to the first electrode.

Further, in the residual chlorine meter of the present invention, the control unit may determine whether or not the elapsed time from the application of the pretreatment voltage is equal to or longer than a predetermined time, and when the elapsed time is equal to or longer than the predetermined time, the pretreatment voltage is applied before the residual chlorine concentration is measured by the measurement unit, and when the elapsed time is less than the predetermined time, the pretreatment voltage is not applied before the residual chlorine concentration is measured by the measurement unit. This configuration also makes it possible to reduce the frequency of applying the pretreatment voltage, thereby speeding up the measurement work and reducing power consumption.

In order to solve the above-mentioned problems, the residual chlorine concentration measuring method of the present invention is a residual chlorine concentration measuring method in which a first electrode that is a working electrode and a second electrode that is a reference electrode or a counter electrode are immersed in a test solution, and the residual chlorine concentration of the test solution is measured based on the voltage between the first electrode and the second electrode. and a measuring step of measuring the residual chlorine concentration of the test liquid based on the voltage between the first electrode and the second electrode.

According to the residual chlorine concentration measuring method of the present invention, as in the residual chlorine meter of the present invention described above, it is possible to remove at least a part of the oxidation-reduction reaction products and the like adhering to the first electrode, and it is possible to suppress the decrease in the measurement accuracy of the residual chlorine concentration due to the adhesion of the oxidation-reduction reaction products and the like to the first electrode.

Further, in the pretreatment step of the residual chlorine concentration measuring method of the present invention, the pretreatment voltage may be swept. This makes it possible to stabilize the measurement accuracy of the residual chlorine concentration of the sample liquid as compared with the case of applying a DC pretreatment voltage.

Further, in the pretreatment step of the residual chlorine concentration measuring method of the present invention, the pretreatment voltage may be swept around 0 V so that the amplitude on the positive side and the amplitude on the negative side are equal to each other. Further, in the pretreatment step of the residual chlorine concentration measuring method of the present invention, the pretreatment voltage may be swept at a constant speed. According to each of these configurations, it is possible to prevent the design of the electric circuit for applying the pretreatment voltage in the pretreatment process from becoming complicated.

According to the present invention, it is possible to suppress the decrease in the measurement accuracy of the residual chlorine concentration due to the adhesion of oxidation-reduction reaction products and the like to the working electrode without requiring trouble for the user, and without incurring an increase in the size, complexity, or price of the residual chlorine meter.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the structure of the residual chlorine meter of the 1st Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is an external view which shows the residual chlorine meter of the 1st Embodiment of this invention. It is a flow chart which shows operation of a residual chlorine meter of a 1st embodiment of the present invention. FIG. 4 is a waveform diagram showing the waveform of the pretreatment voltage in the residual chlorine meter of the first embodiment of the present invention; It is a voltammogram which shows the pretreatment voltage in the residual chlorine meter of the 1st Embodiment of this invention. Fig. 10 is a graph showing the voltage between the working electrode and the reference electrode of the residual chlorine meter when immersed in the test solution, for (A) when neither wiping nor application of pretreatment voltage was performed, and (B) when wiping was performed. 2 is a graph showing the voltage between the working electrode and the reference electrode of the residual chlorine meter when immersed in the test solution, for (A) when neither wiping nor application of the pretreatment voltage was performed, and (B) when the pretreatment voltage was applied. 4 is a table showing the surface analysis results of the working electrode of the residual chlorine meter for each of cases where neither polishing treatment nor application of pretreatment voltage was performed after measurement, when polishing treatment was performed after measurement, and when pretreatment voltage was applied after measurement. 2 is a graph showing changes over time in the voltage between the working electrode and the reference electrode of the residual chlorine meter when immersed in the test solution, for (A) the measurement after rubbing and (B) the measurement after applying the pretreatment voltage. 4 is a graph showing the voltage between the working electrode and the reference electrode of the residual chlorine meter when the test solution is immersed in (A) when the pretreatment voltage is swept, (B) when a positive DC voltage is applied as the pretreatment voltage, and (C) when a negative DC voltage is applied as the pretreatment voltage. It is a flowchart which shows operation|movement of the residual chlorine meter of the 2nd Embodiment of this invention. FIG. 5 is a waveform diagram showing a modification of the pretreatment voltage waveform in the residual chlorine meter of the first or second embodiment of the present invention;

(First embodiment)
First, the residual chlorine meter 1 of the first embodiment of the present invention will be explained. FIG. 1 shows the configuration of a residual chlorine meter 1. As shown in FIG. FIG. 2 shows the appearance of the residual chlorine meter 1. As shown in FIG. As shown in FIG. 1, a residual chlorine meter 1 is a device for measuring the residual chlorine concentration of a test liquid E such as tap water. The residual chlorine meter 1 employs a galvanic system as a method for measuring the residual chlorine concentration. A residual chlorine meter 1 includes a working electrode 2 , a reference electrode 3 , a processing circuit 4 and a power supply circuit 5 . Furthermore, the residual chlorine meter 1 includes a housing 6, operation buttons 7, and a display section 8, as shown in FIG.

In FIG. 2, the housing 6 has a vertically elongated shape when viewed as a whole, and its upper portion is formed in a substantially rectangular parallelepiped shape. In addition, the lower portion of the housing 6 is formed in a cylindrical shape having a smaller diameter than the width and thickness of the upper portion. The working electrode 2 and the reference electrode 3 are attached to the lower end portion of the housing 6 , and the operation buttons 7 and the display section 8 are attached to the upper portion of the housing 6 . Also, the processing circuit 4 and the power supply circuit 5 are accommodated inside the upper portion of the housing 6 . Further, a battery housing portion (not shown) is provided in the upper portion of the housing 6, and a battery 9 is housed in the battery housing portion. In addition, the power supply of the residual chlorine meter 1 is not limited to a battery.

The working electrode 2 is a platinum electrode, a gold electrode, or the like, and is formed in a linear shape, for example. In addition, the working electrode 2 may be formed in a disc shape. The reference electrode 3 is a silver/silver chloride electrode or the like, and is formed linearly. Also, the potential of the reference electrode 3 is set to the reference potential. In this embodiment, the reference potential is 0V.

The processing circuit 4 includes a pretreatment voltage application circuit 11 as a pretreatment section, a measurement circuit 12 as a measurement section, a switch 13, a microcontroller 14 as a control section, and a memory circuit 15 .

The pretreatment voltage application circuit 11 is a circuit that applies a pretreatment voltage between the working electrode 2 and the reference electrode 3 . As will be described later, the residual chlorine meter 1 applies a voltage between the working electrode 2 and the reference electrode 3 before measuring the residual chlorine concentration of the test liquid E. FIG. The process of applying a voltage before this measurement is the "pretreatment", and the voltage applied in this process is the "pretreatment voltage". Further, the pretreatment voltage application circuit 11 has a function of sweeping the pretreatment voltage.

The measurement circuit 12 is a circuit that measures the residual chlorine concentration of the test liquid E based on the voltage between the working electrode 2 and the reference electrode 3 . For example, the measurement circuit 12 analog-to-digital converts the voltage between the working electrode 2 and the reference electrode 3, and specifies the residual chlorine concentration value corresponding to the digitized voltage value by referring to a data table in which the correspondence relationship between the voltage value between the electrodes and the residual chlorine concentration value is recorded in advance, or by a method of calculating using a predetermined formula or the like. The measuring circuit 12 then outputs the specified residual chlorine concentration value to the microcontroller 14 .

The switch 13 is a circuit that switches between a path for applying a pretreatment voltage between the working electrode 2 and the reference electrode 3 and a path for measuring the residual chlorine concentration based on the voltage between the working electrode 2 and the reference electrode 3. Specifically, when the contact a and the contact c are connected in the switch 13, a path for applying the pretreatment voltage from the pretreatment voltage application circuit 11 to the working electrode 2 and the reference electrode 3 is formed. On the other hand, when the switch 13 connects the contact b and the contact c, the measurement circuit 12 forms a path for measuring the residual chlorine concentration based on the voltage between the working electrode 2 and the reference electrode 3 .

The microcontroller 14 is a device for controlling the pretreatment voltage application circuit 11, the measurement circuit 12, and the switch 13, and has an arithmetic processing circuit and the like. The microcontroller 14 outputs a switching control signal to the switch 13, and the switch 13 can switch between a state in which the contacts a and c are connected and a state in which the contacts b and c are connected. The microcontroller 14 can also output a pretreatment control signal to the pretreatment voltage application circuit 11 to start outputting the pretreatment voltage. The microcontroller 14 can also output a measurement control signal to the measurement circuit 12 to initiate measurement of the residual chlorine concentration. Further, when the operation button 7 is pressed by the user, the microcontroller 14 starts preprocessing in response to the depression, and performs measurement processing after finishing the preprocessing. Further, the microcontroller 14 can cause the display unit 8 to display the measurement result of the residual chlorine concentration. The display unit 8 is, for example, a liquid crystal display. The memory circuit 15 includes a semiconductor memory element and stores data and the like used for processing by the microcontroller 14 .

The power supply circuit 5 is a circuit that supplies power obtained from the battery 9 to the pretreatment voltage application circuit 11 , the measurement circuit 12 , the switch 13 , the microcontroller 14 , the memory circuit 15 , the circuits of the operation buttons 7 and the display section 8 .

FIG. 3 shows the operation of the residual chlorine meter 1. FIG. When measuring the residual chlorine concentration of the test liquid E, the user puts the lower end of the residual chlorine meter 1 into the test liquid E, and immerses the working electrode 2 and the reference electrode 3 in the test liquid E. Then, the user presses the operation button 7 while the working electrode 2 and the reference electrode 3 are immersed in the sample liquid E.

The microcontroller 14 of the residual chlorine meter 1 detects pressing of the operation button 7 as shown in step S1 in FIG. 3 (step S1: YES). Subsequently, the microcontroller 14 outputs a switching control signal to the switch 13 to connect the contacts a and c of the switch 13 . Subsequently, the microcontroller 14 outputs a pretreatment control signal to the pretreatment voltage applying circuit 11 to start outputting the pretreatment voltage. This starts the application of the pretreatment voltage between the working electrode 2 and the reference electrode 3 (step S2: pretreatment step).

Here, FIG. 4 shows the waveform of the pretreatment voltage. Also, FIG. 5 shows a voltammogram of the pretreatment voltage. The pretreatment voltage applying circuit 11 sweeps the pretreatment voltage as shown in FIGS. 4 and 5, for example. That is, the pretreatment voltage application circuit 11 sweeps the pretreatment voltage around 0 V so that the amplitude on the positive side and the amplitude on the negative side are equal to each other. In this embodiment, for example, the pretreatment voltage has a positive peak value of 1.5V and a negative peak value of -1.5V. Also, the pretreatment voltage applying circuit 11 sweeps the pretreatment voltage at a constant speed. In this embodiment, for example, the sweep rate of the pretreatment voltage is 0.5 V/sec. In this way, by sweeping the pretreatment voltage so that the amplitude on the positive side and the amplitude on the negative side are equal to each other around 0 V, or by sweeping the pretreatment voltage at a constant speed, the design of the pretreatment voltage applying circuit 11 can be prevented from becoming complicated.

Further, the pretreatment voltage applying circuit 11 sweeps the pretreatment voltage in a constant pattern. The pattern of the pretreatment voltage in this embodiment is as follows. That is, as shown in FIG. 4, the voltage value at the start of the pretreatment voltage is 0V. Subsequently, the pretreatment voltage is increased from 0 V at a rate of 0.5 V/s for 3 seconds. As a result, the voltage value of the pretreatment voltage reaches 1.5V. Subsequently, the pretreatment voltage is decreased from 1.5 V at a rate of 0.5 V/s for 6 seconds. As a result, the voltage value of the pretreatment voltage reaches -1.5V. Subsequently, the pretreatment voltage is increased from -1.5 V at a rate of 0.5 V/s for 3 seconds. As a result, the voltage value of the pretreatment voltage becomes 0V. After sweeping the pretreatment voltage in this pattern for 12 seconds, the pretreatment voltage application circuit 11 stops outputting the pretreatment voltage. As a result, the waveform of the pretreatment voltage becomes a waveform corresponding to one cycle of the triangular wave.

After the output of the pretreatment voltage is stopped, the microcontroller 14 outputs a switching control signal to the switching device 13 to connect the contact b and the contact c of the switching device 13 . Subsequently, the microcontroller 14 outputs a measurement control signal to the measurement circuit 12 to start measuring the residual chlorine concentration of the sample liquid E. FIG. The measurement circuit 12 measures the residual chlorine concentration of the test liquid E based on the voltage between the working electrode 2 and the reference electrode 3, and outputs the measured residual chlorine concentration value to the microcontroller 14 (step S3: measurement step).

Subsequently, the microcontroller 14 displays the measurement result of the residual chlorine concentration by the measurement circuit 12 on the display section 8 (step S4).

According to the residual chlorine meter 1 of the first embodiment of the present invention, by applying a pretreatment voltage between the working electrode 2 and the reference electrode 3, it is possible to remove at least part of the oxidation-reduction reaction products and the like attached to the working electrode 2 due to the measurement of the residual chlorine concentration performed last time or earlier. Then, by measuring the residual chlorine concentration after finishing the application of the pretreatment voltage, it is possible to suppress the decrease in the measurement accuracy of the residual chlorine concentration due to the adhesion of oxidation-reduction reaction products and the like to the working electrode 2. This effect of the residual chlorine meter 1 was confirmed by several experiments described below.

(First experiment)
First, an experiment was conducted to measure the voltage between the working electrode of the residual chlorine meter and the reference electrode when immersed in the test solution, for each of the cases where the working electrode was neither rubbed nor the pretreatment voltage was applied, the working electrode was rubbed and the pretreatment voltage was applied, respectively. This experiment is called "first experiment".

In the first experiment, an experimental galvanic residual chlorine meter was used, which had the same working electrode, reference electrode, and measurement circuit as the residual chlorine meter 1 of the first embodiment of the present invention, and was provided with a function capable of outputting the voltage value between the working electrode and the reference electrode as data to the outside. In conducting the first experiment, six such residual chlorine meters were prepared, the working electrode and the reference electrode of which were immersed in a test solution such as tap water for about ten seconds, removed from the test solution, and left for about one year. These six residual chlorine meters are referred to as residual chlorine meters M1 to M6. Furthermore, in conducting the first experiment, pure water, regulated water with a residual chlorine concentration of about 0.2 mg/L, regulated water with a residual chlorine concentration of about 0.4 mg/L, and regulated water with a residual chlorine concentration of about 0.8 mg/L were prepared. Then, using the residual chlorine meters M1 to M3, the voltage between the working electrode and the reference electrode when immersed in the test solution when neither the working electrode is rubbed nor the pretreatment voltage is applied, and the voltage between the working electrode and the reference electrode when the working electrode is rubbed and immersed in the test solution were measured. Further, using residual chlorine meters M4 to M6, the voltage between the working electrode and the reference electrode when immersed in the test solution when neither the working electrode is rubbed nor the pretreatment voltage is applied, and the voltage when the working electrode and the reference electrode are immersed in the test solution when the pretreatment voltage is applied were measured.

The first experiment will be described more specifically. First, the working electrode and the reference electrode of the residual chlorine meter M1 are immersed in the test solution, and the voltage between both electrodes is measured in that state, sequentially and continuously for the above four types of test solutions (step 1-1). Next, the working electrode of the residual chlorine meter M1 was thoroughly wiped with a melamine sponge or the like (step 1-2). Immediately after wiping, the working electrode and the reference electrode of the residual chlorine meter M1 are immersed in the test solution, and the voltage between both electrodes is measured in that state for the above four types of test solutions. Next, steps 1-1 to 1-3 were performed using the residual chlorine meter M2, and then steps 1-1 to 1-3 were performed using the residual chlorine meter M3.

In addition, the working electrode and the reference electrode of the residual chlorine meter M4 are immersed in the test liquid, and the voltage between both electrodes is measured in that state, and the above four types of test liquids are sequentially and continuously performed (step 1-4). Next, the working electrode and the reference electrode of the residual chlorine meter M4 were immersed in one of the above four types of test solutions, and in this state, an external device such as a potentiostat was used to apply a pretreatment voltage with a sweep pattern shown in FIG. 4 between the working electrode and the reference electrode of the residual chlorine meter M4 (step 1-5). Immediately after finishing the application of the pretreatment voltage, the working electrode and the reference electrode of the residual chlorine meter M4 were immersed in the test solution, and the voltage between both electrodes was measured in that state. Next, steps 1-4 to 1-6 were performed using the residual chlorine meter M5, and then steps 1-4 to 1-6 were performed using the residual chlorine meter M6.

The reason for performing steps 1-1 to 1-3 three times using three residual chlorine meters M1 to M3 and performing steps 1-4 to 1-6 three times using three residual chlorine meters M4 to M6 is to confirm the accuracy of the experiment.

FIG. 6A shows the measurement results of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M1 to M3 obtained in step 1-1. These are the measurement results of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M1 to M3 when the working electrode was not rubbed and the pretreatment voltage was not applied. The dashed line in FIG. 6(A) indicates the voltage value (upper limit voltage value U) between the working electrode and the reference electrode when immersed in the test solution, which corresponds to the upper limit of the error range allowed for the residual chlorine meter. In addition, the two-dot chain line in FIG. 6(A) indicates the voltage value (lower limit voltage value L) between the working electrode and the reference electrode when the test solution is immersed, which corresponds to the lower limit of the error range allowed for the residual chlorine meter. 6(B), 7(A), and 7(B) also show a dashed line indicating the upper limit voltage value U and a two-dot chain line indicating the lower limit voltage value L. FIG. As can be seen from FIG. 6(A), the voltages between the working electrodes and the reference electrodes of the residual chlorine meters M1 to M3 are all lower than the lower limit voltage value L for all the residual chlorine concentrations of the four types of test liquids used in this experiment. That is, when the residual chlorine concentration of the sample liquid is measured without rubbing the working electrode or applying the pretreatment voltage, the correct measurement result of the residual chlorine concentration cannot be obtained.

FIG. 6B shows the measurement results of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M1 to M3 obtained in step 1-3. These are the measurement results of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M1 to M3 when the working electrode was rubbed and immersed in the sample liquid. As can be seen from FIG. 6(B), the voltages between the working electrodes and the reference electrodes of the residual chlorine meters M1 to M3 are all at least the lower limit voltage value L and below the upper limit voltage value U at all of the residual chlorine concentrations of the four types of test liquids used in this experiment. That is, when the residual chlorine concentration of the test liquid is measured after the working electrode is rubbed, the correct measurement result of the residual chlorine concentration can be obtained.

As can be seen from a comparison of FIGS. 6A and 6B, by rubbing the working electrode, it is possible to remove at least a portion of the redox reaction products and the like that adhered to the working electrode when the residual chlorine concentration was measured last time or before. By measuring the residual chlorine concentration after rubbing, it is possible to suppress a decrease in the measurement accuracy of the residual chlorine concentration due to the adhesion of the redox reaction products and the like to the working electrode.

FIG. 7(A) shows the measurement results of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M4 to M6 obtained in step 1-4. These are the measurement results of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M4 to M6 when the working electrode was not rubbed and the pretreatment voltage was not applied. As can be seen from FIG. 7(A), the voltages between the working electrodes and the reference electrodes of the residual chlorine meters M4 to M6 are all below the lower limit voltage value L for all the residual chlorine concentrations of the four types of test liquids used in this experiment. That is, when the residual chlorine concentration of the test solution is measured without rubbing the working electrode or applying the pretreatment voltage, the correct measurement result of the residual chlorine concentration cannot be obtained. It was also confirmed for each of the residual chlorine meters M4 to M6.

FIG. 7B shows the measurement results of the voltage between the working electrode and the reference electrode of each residual chlorine meter M4 to M6 obtained in step 1-6. These are the measurement results of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M4 to M6 when the pretreatment voltage is applied, when the test solution is immersed. As can be seen from FIG. 7(B), the voltages between the working electrodes and the reference electrodes of the residual chlorine meters M4 to M6 are all at least the lower limit voltage value L and below the upper limit voltage value U at all of the residual chlorine concentrations of the four types of test liquids used in this experiment. That is, when the residual chlorine concentration of the sample liquid is measured after the pretreatment voltage is applied, the correct measurement result of the residual chlorine concentration can be obtained.

7(A) and 7(B), by applying the pretreatment voltage between the working electrode and the reference voltage, it is possible to remove at least a part of the oxidation-reduction reaction products and the like attached to the working electrode as a result of the measurement of the residual chlorine concentration carried out previously or before. By measuring the residual chlorine concentration after the application of the pretreatment voltage, it is possible to suppress the decrease in the measurement accuracy of the residual chlorine concentration due to the adhesion of the oxidation-reduction reaction products and the like to the working electrode.

As described above, in the first experiment, it was confirmed that, in the residual chlorine meter 1 of the first embodiment of the present invention, by measuring the residual chlorine concentration of the test liquid E after applying the pretreatment voltage between the working electrode 2 and the reference electrode 3, it was possible to suppress the decrease in the measurement accuracy of the residual chlorine concentration to the same extent as when measuring the residual chlorine concentration of the test liquid E after rubbing the working electrode 2.

According to the residual chlorine meter 1 of the first embodiment of the present invention, by applying a pretreatment voltage between the working electrode 2 and the reference electrode 3 before measuring the residual chlorine concentration of the test liquid E, it is possible to suppress a decrease in the measurement accuracy of the residual chlorine concentration due to adhesion of redox reaction products and the like to the working electrode 2. Therefore, it is possible to eliminate the work of wiping off oxidation-reduction reaction products and the like adhering to the working electrode 2 with a soft cloth, melamine sponge, or the like before measurement. In addition, in order to polish the working electrode 2 with the polishing beads, a large-scale device such as a device for circularly moving the working electrode 2 with a motor or a device for pouring the sample liquid E into a container containing the polishing beads is not required, and the residual chlorine meter 1 can be prevented from becoming larger, more complicated, and more expensive.

(Surface analysis of working electrode)
For reference, the results of surface analysis of the working electrode are shown for each of cases in which neither polishing treatment of the working electrode nor application of pretreatment voltage was performed, polishing treatment of the working electrode was performed, and application of pretreatment voltage was performed. X-ray photoelectric spectroscopy (XPS) was adopted as a technique for surface analysis.

Specifically, three experimental galvanic residual chlorine meters having the same working electrode (platinum electrode), reference electrode, and measurement circuit as the residual chlorine meter 1 of the first embodiment of the present invention were prepared by immersing the working electrode and the reference electrode in a test solution such as tap water for ten seconds or so, taking them out of the test solution, and leaving them for about one year. These three residual chlorine meters are referred to as residual chlorine meters M11 to M13. Then, for the residual chlorine meter M11, after the working electrode and the reference electrode were immersed in tap water for ten seconds or so, the surface of the working electrode was analyzed without polishing the working electrode or applying a pretreatment voltage between the working electrode and the reference electrode. In addition, for the residual chlorine meter M12, after the working electrode and the reference electrode were immersed in tap water for 10 seconds or so, the working electrode was polished using an abrasive (diamond paste) (polishing treatment), and immediately after that, the surface of the working electrode was analyzed. In addition, for the residual chlorine meter M13, the working electrode and the reference electrode were immersed in tap water for ten seconds or so, a pretreatment voltage with a sweep pattern shown in FIG. 4 was applied between the working electrode and the reference electrode during immersion, and the surface of the working electrode was analyzed immediately after immersion.

FIG. 8 shows the results of surface analysis of the working electrodes of the residual chlorine meters M11 to M13. As can be seen from FIG. 8, the ratio of platinum (Pt) on the surface of the working electrode of the residual chlorine meter M11 is 11.1%, while the ratio of platinum on the surface of the working electrode of the residual chlorine meter M12 is 36.3%. That is, the proportion of platinum on the surface of the working electrode of the residual chlorine meter M12 is greater than the proportion of platinum on the surface of the working electrode of the residual chlorine meter M11. This means that part of the redox reaction products and the like adhering to the surface of the working electrode was removed by subjecting the working electrode to the polishing treatment.

As can be seen from FIG. 8, the ratio of platinum on the surface of the working electrode of the residual chlorine meter M11 is 11.1%, while the ratio of platinum on the surface of the working electrode of the residual chlorine meter M13 is 22.4%. That is, the proportion of platinum on the surface of the working electrode of the residual chlorine meter M13 is greater than the proportion of platinum on the surface of the working electrode of the residual chlorine meter M11. This means that the application of the pretreatment voltage between the working electrode and the reference electrode partially removed redox reaction products and the like attached to the surface of the working electrode.

Further, as can be seen from FIG. 8, the ratio of platinum on the surface of the working electrode of the residual chlorine meter M13 is close to the ratio of platinum on the surface of the working electrode of the residual chlorine meter M12. This means that an effect similar to the effect of removing redox reaction products and the like obtained by polishing the working electrode of a residual chlorine meter can be obtained by applying a pretreatment voltage between the working electrode and the reference electrode of the residual chlorine meter.

(Second experiment)
Next, an experiment was conducted in which the voltage between the working electrode and the reference electrode when immersed in the test solution was measured multiple times at predetermined time intervals for each of the residual chlorine meter in which the working electrode was rubbed and the residual chlorine meter in which a pretreatment voltage was applied between the working electrode and the reference electrode. This experiment is called "second experiment".

In the second experiment, as in the first experiment, an experimental galvanic residual chlorine meter was used, which had the same working electrode, reference electrode, and measurement circuit as the residual chlorine meter 1 of the first embodiment of the present invention, and was provided with a function capable of outputting the voltage value between the working electrode and the reference electrode as data to the outside. In conducting the second experiment, 10 such residual chlorine meters were prepared, the working electrode and the reference electrode of which were immersed in a test liquid such as tap water for about ten seconds, removed from the test liquid, and left for about one year. These ten residual chlorine meters are referred to as residual chlorine meters M21 to M30. Furthermore, in conducting the second experiment, conditioned water with a residual chlorine concentration of about 0.2 mg/L, conditioned water with a residual chlorine concentration of about 0.4 mg/L, and regulated water with a residual chlorine concentration of about 0.8 mg/L were prepared. Then, using residual chlorine meters M21 to M25, the voltage between the working electrode and the reference electrode after the working electrode was rubbed and immersed in the test solution was measured multiple times at predetermined time intervals. In addition, using residual chlorine meters M26 to M30, the voltage between the working electrode and the reference electrode after the pretreatment voltage was applied and the electrode being immersed in the test solution was measured multiple times at predetermined time intervals.

The second experiment will be described more specifically. First, the working electrode of the residual chlorine meter M21 was thoroughly wiped with a melamine sponge or the like (step 2-1). Immediately after wiping, the working electrode and reference electrode of the residual chlorine meter M21 are immersed in the test solution, and the voltage between both electrodes is measured in that state for the above three types of test solutions. Next, the residual chlorine meter M21 was immediately removed from the liquid to be tested and left in the atmosphere (step 2-3). Next, on the same day, using residual chlorine meters M22 to M25, Steps 2-1 to 2-3 were sequentially and continuously performed. Next, 1 day, 7 days, 14 days, 21 days and 28 days after the day when step 2-1 was performed using the residual chlorine meters M21 to M25, only steps 2-2 and 2-3 were sequentially and continuously performed using the residual chlorine meters M21 to M25.

In addition, the working electrode and the reference electrode of the residual chlorine meter M26 were immersed in one of the three types of test liquids, and in that state, an external device such as a potentiostat was used to apply a pretreatment voltage with a sweep pattern shown in FIG. 4 between the working electrode and the reference electrode of the residual chlorine meter M26 (step 2-4). Immediately after finishing the application of the pretreatment voltage, the working electrode and the reference electrode of the residual chlorine meter M26 were immersed in the test solution, and the voltage between both electrodes was measured in that state. Next, the residual chlorine meter M26 was immediately taken out of the liquid to be tested and left in the atmosphere (step 2-6). Next, on the same day, using residual chlorine meters M27 to M30, Steps 2-4 to 2-6 were sequentially and continuously performed. Next, 1 day, 7 days, 14 days, 21 days and 28 days after the day when step 2-4 was performed using the residual chlorine meters M26 to M30, only steps 2-5 and 2-6 were sequentially and continuously performed using the residual chlorine meters M26 to M30.

FIG. 9A shows the average value of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M21 to M25 obtained in step 2-2 when immersed in the test solution, calculated for each elapsed day and for each residual chlorine concentration of the test solution, and shows the change in the average value according to the elapsed days. In addition, FIG. 9B shows the average value of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M26 to M30 obtained in step 2-5 when immersed in the test solution, calculated for each elapsed day and for each residual chlorine concentration of the test solution, and shows the change in the average value according to the elapsed days. The two-dot chain lines in FIGS. 9A and 9B indicate the voltage values (lower limit voltage values La, Lb, and Lc) between the working electrode and the reference electrode when the working electrode and the reference electrode are immersed in the test solution, corresponding to the lower limit of the error range allowed for the residual chlorine meter, for each residual chlorine concentration. The lower limit voltage value La is the lower limit voltage value when the working electrode and the reference electrode are immersed in a test solution having a residual chlorine concentration of about 0.2 mg/L. The lower limit voltage value Lb is the lower limit voltage value when the working electrode and the reference electrode are immersed in a test solution having a residual chlorine concentration of about 0.4 mg/L. The lower limit voltage value Lc is the lower limit voltage value when the working electrode and the reference electrode are immersed in a test solution having a residual chlorine concentration of about 0.8 mg/L.

As can be seen from FIG. 9A, in the residual chlorine meters M21 to M25 whose working electrodes were wiped off, the voltage between the working electrode and the reference electrode during immersion in the test solution fell below the respective lower limit voltage values La, Lb, and Lc for all residual chlorine concentrations just one day after the working electrode and the reference electrode were immersed in the test solution on the start day of the second experiment. On the other hand, as can be seen from FIG. 9B, in the residual chlorine meters M26 to M30 in which a pretreatment voltage was applied between the working electrode and the reference electrode, the working electrode and the reference electrode were immersed in the test solution on the start day of the second experiment, and after 21 days had passed, the voltage between the working electrode and the reference electrode during immersion in the test solution was equal to or higher than the lower limit voltage values La, Lb, and Lc for all residual chlorine concentrations. As can be seen from a comparison of FIGS. 9(A) and 9(B), applying a pretreatment voltage between the working electrode and the reference electrode of the residual chlorine meter lasts longer than rubbing the working electrode of the residual chlorine meter to suppress the reduction in measurement accuracy of the residual chlorine concentration due to adhesion of oxidation-reduction reaction products and the like to the working electrode.

As described above, in the second experiment, it was confirmed that, in the residual chlorine meter 1 of the first embodiment of the present invention, by applying the pretreatment voltage between the working electrode 2 and the reference electrode 3, the effect of suppressing the decrease in measurement accuracy of the residual chlorine concentration caused by the adhesion of oxidation-reduction reaction products and the like to the working electrode 2 can be maintained for a long time.

(Third experiment)
Next, an experiment was conducted to measure the voltage between the working electrode and the reference electrode of the residual chlorine meter when the test solution was immersed in each of the cases of sweeping the pretreatment voltage, applying a positive DC voltage as the pretreatment voltage, and applying a negative DC voltage as the pretreatment voltage. This experiment is called "third experiment".

In the third experiment, as in the first experiment, an experimental galvanic residual chlorine meter was used, which had the same working electrode, reference electrode, and measurement circuit as the residual chlorine meter 1 of the first embodiment of the present invention, and was provided with a function capable of outputting the voltage value between the working electrode and the reference electrode as data to the outside. In conducting the third experiment, nine such residual chlorine meters were prepared in which the working electrode and the reference electrode were immersed in a test solution such as tap water for about ten seconds, removed from the test solution, and left for about one year. These nine residual chlorine meters are referred to as residual chlorine meters M41 to M49. Furthermore, in conducting the third experiment, pure water, regulated water with a residual chlorine concentration of about 0.3 mg/L, and regulated water with a residual chlorine concentration of about 0.9 mg/L were prepared as liquids to be tested. Then, using residual chlorine meters M41 to M43, the voltage between the working electrode and the reference electrode when the pretreatment voltage was swept was measured during immersion in the test solution. In addition, using residual chlorine meters M44 to M46, the voltage between the working electrode and the reference electrode during immersion in the test solution was measured when a positive DC voltage was applied as the pretreatment voltage. In addition, using residual chlorine meters M47 to M49, the voltage between the working electrode and the reference electrode during immersion in the test solution was measured when a negative DC voltage was applied as the pretreatment voltage.

The third experiment will be described more specifically. First, the working electrode and the reference electrode of the residual chlorine meter M41 were immersed in one of the above three test liquids, and in this state, an external device such as a potentiostat was used to apply a pretreatment voltage with a sweep pattern shown in FIG. 4 between the working electrode and the reference electrode of the residual chlorine meter M41 (step 3-1). The positive side peak value of this pretreatment voltage was 1.5 V, the negative side peak value was -1.5 V, and the application time was 12 seconds. Immediately after finishing the application of the pretreatment voltage, the working electrode and the reference electrode of the residual chlorine meter M41 were immersed in the test solution, and in that state, the operation of measuring the voltage between both electrodes was continuously performed for the above three types of test solutions (step 3-2). Next, steps 3-1 and 3-2 were performed using the residual chlorine meter M42, and then steps 3-1 and 3-2 were performed using the residual chlorine meter M43.

In addition, the working electrode and the reference electrode of the residual chlorine meter M44 were immersed in one of the above three types of test liquids, and in that state, an external device such as a potentiostat was used to apply a DC voltage of 1.5 V as a pretreatment voltage between the working electrode and the reference electrode of the residual chlorine meter M44 for 12 seconds (step 3-3). Immediately after finishing the application of the pretreatment voltage, the working electrode and the reference electrode of the residual chlorine meter M44 were immersed in the test solution, and the voltage between the two electrodes was measured in that state. Next, steps 3-3 and 3-4 were performed using the residual chlorine meter M45, and then steps 3-3 and 3-4 were performed using the residual chlorine meter M46.

In addition, the working electrode and the reference electrode of the residual chlorine meter M47 were immersed in one of the above three types of test liquids, and in this state, using an external device such as a potentiostat, a DC voltage of -1.5 V was applied as a pretreatment voltage between the working electrode and the reference electrode of the residual chlorine meter M47 for 12 seconds (step 3-5). Immediately after finishing the application of the pretreatment voltage, the working electrode and the reference electrode of the residual chlorine meter M47 were immersed in the test solution, and in that state, the operation of measuring the voltage between both electrodes was sequentially and continuously performed for the above three types of test solutions (step 3-6). Next, steps 3-5 and 3-6 were performed using a residual chlorine meter M48, and then steps 3-5 and 3-6 were performed using a residual chlorine meter M49.

FIG. 10(A) shows the measurement results of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M41 to M43 obtained in step 3-2 when the test solution is immersed. These are the measurement results of the voltage between the working electrode and the reference electrode of the residual chlorine meter when the pretreatment voltage is swept, when the test solution is immersed. The dashed line in FIG. 10(A) indicates the voltage value (upper limit voltage value U) between the working electrode and the reference electrode when immersed in the test solution, which corresponds to the upper limit of the error range allowed for the residual chlorine meter. In addition, the two-dot chain line in FIG. 10(A) indicates the voltage value (lower limit voltage value L) between the working electrode and the reference electrode when the test solution is immersed, which corresponds to the lower limit of the error range allowed for the residual chlorine meter. 10A indicates a voltage value exactly intermediate between the upper limit voltage value U and the lower limit voltage value L. In FIG. Also in FIGS. 10B and 10C, a dashed line indicating the upper limit voltage value U, a two-dot chain line indicating the lower limit voltage value L, and a dashed-dotted line indicating exactly between the upper limit voltage value U and the lower limit voltage value L are drawn. As can be seen from FIG. 10(A), the voltages between the working electrodes and the reference electrodes of the residual chlorine meters M41 to M43 are all the lower limit voltage value L or higher and the upper limit voltage value U or lower for all of the residual chlorine concentrations of the three test liquids used in this experiment. Furthermore, most of the voltages between the working electrodes and the reference electrodes of the residual chlorine meters M41 to M43 are concentrated near the middle between the lower limit voltage value L and the upper limit voltage value U.

FIG. 10(B) shows the measurement results of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M44 to M46 obtained in step 3-4 when the sample liquid is immersed. These are the measurement results of the voltage between the working electrode and the reference electrode of the residual chlorine meter when the test solution is immersed, when a positive DC voltage is applied as the pretreatment voltage. As can be seen from FIG. 10(B), the voltages between the working electrodes and the reference electrodes of the residual chlorine meters M44 to M46 are all equal to or higher than the lower limit voltage value L and equal to or lower than the upper limit voltage value U for all of the residual chlorine concentrations of the three test liquids used in this experiment. However, some of the voltages between the working electrodes and the reference electrodes of the residual chlorine meters M44 to M46 are lower than exactly midway between the lower limit voltage value L and the upper limit voltage value U and are close to the lower limit voltage value L.

FIG. 10(C) shows the measurement result of the voltage between the working electrode and the reference electrode of each of the residual chlorine meters M47 to M49 obtained in step 3-6 when the sample liquid is immersed. These are the measurement results of the voltage between the working electrode and the reference electrode of the residual chlorine meter during immersion in the test solution when a negative DC voltage is applied as the pretreatment voltage. As can be seen from FIG. 10(C), part of the voltage between the working electrode and the reference electrode of the residual chlorine meters M47 to M49 exceeds the upper limit voltage value U.

A comparison of FIGS. 10A to 10C reveals the following. That is, when the pretreatment voltage is swept, the variation in the voltage between the working electrode and the reference electrode of the residual chlorine meter when measuring the residual chlorine concentration of the test solution is small, and the voltage is stable between the upper limit voltage value U and the lower limit voltage value L. On the other hand, when a DC pretreatment voltage is applied, the variation in voltage between the working electrode and the reference electrode of the residual chlorine meter during measurement of the residual chlorine concentration of the test solution is large, the voltage is unstable, and the voltage may deviate from between the upper limit voltage value U and the lower limit voltage value L.

As described above, according to the third experiment, by sweeping the pretreatment voltage as in the residual chlorine meter 1 of the first embodiment of the present invention, it was confirmed that the measurement accuracy of the residual chlorine concentration of the test liquid E can be further improved.

(Second embodiment)
Next, a residual chlorine meter according to a second embodiment of the present invention will be described. The residual chlorine meter 1 of the first embodiment of the present invention described above applies a pretreatment voltage before measurement each time the residual chlorine concentration of the test liquid E is measured. On the other hand, in the residual chlorine meter of the second embodiment of the present invention, the pretreatment voltage before measurement is applied once every time the measurement of the residual chlorine concentration of the test liquid E is performed a predetermined number of times (2 or more).

The hardware configuration of the residual chlorine meter of the second embodiment is the same as the hardware configuration of the residual chlorine meter 1 of the first embodiment shown in FIG. Further, the microcontroller 14 of the residual chlorine meter of the second embodiment is added with a function of controlling the application of the pretreatment voltage based on the number of measurements of the residual chlorine concentration. That is, the microcontroller 14 of the residual chlorine meter of the second embodiment determines whether or not the number of measurements of the residual chlorine concentration after the application of the pretreatment voltage is a predetermined number or more. When the number of measurements is the predetermined number or more, the pretreatment voltage is applied before the next measurement of the residual chlorine concentration. Further, the memory circuit 15 of the residual chlorine meter of the second embodiment stores a measurement count value, which is a count value indicating the number of measurements of the residual chlorine concentration after the application of the pretreatment voltage. Note that the initial value of the number of measurements is 0 in this embodiment.

FIG. 11 shows the operation of the residual chlorine meter of the second embodiment of the invention. In FIG. 11, when the user immerses the working electrode 2 and the reference electrode 3 in the test solution E and presses the operation button 7, the microcontroller 14 detects the pressing of the operation button 7 (step S11: YES), and then reads out the number of measurements from the memory circuit 15 (step S12). Subsequently, the microcontroller 14 determines whether or not the read measurement count value is greater than or equal to a preset count reference value (step S13). The frequency reference value is, for example, 2 or more and is set in advance. It should be noted that the user may arbitrarily set the frequency reference value.

As a result of this determination, if the measurement count value is equal to or greater than the reference count value (step S13: YES), the microcontroller 14 sets the measurement count value to an initial value (step S14). Subsequently, the microcontroller 14 controls the switch 13 to connect the contact a and the contact c of the switch 13, and then controls the pretreatment voltage application circuit 11 to start applying the pretreatment voltage between the working electrode 2 and the reference electrode 3 (step S15: pretreatment step). Under the control of the microcontroller 14, the pretreatment voltage application circuit 11 starts outputting the pretreatment voltage, sweeps the pretreatment voltage for 12 seconds according to the sweep pattern shown in FIG. 4, and then stops applying the pretreatment voltage.

After the output of the pretreatment voltage is stopped, the microcontroller 14 controls the switch 13 to connect the contact b and the contact c of the switch 13, and then controls the measurement circuit 12 to start measuring the residual chlorine concentration of the test liquid E. The measurement circuit 12 measures the residual chlorine concentration of the test liquid E, and outputs the measured residual chlorine concentration value to the microcontroller 14 (step S16: measurement step).

On the other hand, as a result of the determination in step S13, if the number of measurements is not equal to or greater than the standard number of measurements (step S13: NO), the microcontroller 14 immediately connects the contact b and the contact c of the switch 13 without performing the process of setting the number of measurements to the initial value and the control of applying the pretreatment voltage, and causes the measurement circuit 12 to start measuring the residual chlorine concentration of the test liquid E. The measurement circuit 12 measures the residual chlorine concentration of the test liquid E, and outputs the measured residual chlorine concentration value to the microcontroller 14 (step S16: measurement step).

Subsequently, the microcontroller 14 displays the measurement result of the residual chlorine concentration output from the measurement circuit 12 on the display section 8 (step S17). Subsequently, the microcontroller 14 increases the number of measurements stored in the storage circuit 15 by 1 (step S18).

In the residual chlorine meter of the second embodiment of the present invention, for example, when the reference number of times is set to 5 and the measurement of the residual chlorine concentration is performed six times after the application of the pretreatment voltage, the first measurement of the residual chlorine concentration is performed immediately after the application of the pretreatment voltage, so the application of the pretreatment voltage is performed immediately before the first measurement of the residual chlorine concentration. Next, the pretreatment voltage is not applied immediately before the second, third, fourth and fifth residual chlorine concentration measurements. Next, the pretreatment voltage is applied immediately before the sixth residual chlorine concentration measurement.

According to the residual chlorine meter of the second embodiment of the present invention, since the pretreatment voltage is applied less frequently, it is possible to speed up the measurement operation while suppressing deterioration in the measurement accuracy of the residual chlorine concentration due to the adhesion of oxidation-reduction reaction products and the like to the working electrode 2, as well as to reduce power consumption and extend the life of the battery 9.

In each of the above embodiments, the case of applying a triangular wave pretreatment voltage as shown in FIG. 4 was taken as an example, but the phase, sweep speed, magnitude of peak value, number of cycles, application time, waveform, etc. of the pretreatment voltage are not limited. For example, as shown in (A), (B), or (C) of FIG. 12, the phases of the pretreatment voltages (sweep start voltage and sweep end voltage) may be changed. In each of the above embodiments, the sweep speed of the pretreatment voltage was set to 0.5 V/sec, but the sweep speed of the pretreatment voltage may be slower or faster than this. In each of the above-described embodiments, the positive peak value of the pretreatment voltage is 1.5 V and the negative peak value is −1.5 V, but each peak value can be adjusted as appropriate. In each of the above embodiments, the pretreatment voltage for one cycle of the waveform is applied, but the pretreatment voltage for two or more cycles of the waveform may be applied. Also, the waveform of the pretreatment voltage may be a sine wave.

Also, the pretreatment voltage may be a positive or negative DC voltage. As discussed above with reference to FIG. 10, when a DC pretreatment voltage is applied, the voltage between the working electrode and the reference electrode of the residual chlorine meter may become unstable when measuring the residual chlorine concentration compared to when the pretreatment voltage is swept.

Further, in each of the above embodiments, the case where the application of the pretreatment voltage is automatically shifted to the measurement of the residual chlorine concentration is taken as an example, but the application of the pretreatment voltage may be manually transferred to the measurement of the residual chlorine concentration. Alternatively, only the application of the pretreatment voltage may be performed according to the user's operation.

Also, when measuring the residual chlorine concentration, the measuring circuit 12 may apply a bias voltage between the working electrode 2 and the reference electrode 3 . This bias voltage is different from the voltage applied to measure the residual chlorine concentration in the polarographic residual chlorine meter.

In the above-described embodiment, the case of applying the present invention to a portable type residual chlorine meter as shown in FIG. 2 was taken as an example, but the present invention can also be applied to, for example, a stationary residual chlorine meter in which a working electrode and a reference electrode are fixed to a tap water pipe or a water tank, and the residual chlorine concentration of tap water flowing through the pipe or stored in the water tank is periodically measured.

Further, in the residual chlorine meter of the second embodiment, in determining whether or not to apply the pretreatment voltage based on the number of measurements of the residual chlorine concentration after the application of the pretreatment voltage, the reference number of times, which is the basis for the determination, may be changed based on the measured value obtained by actually measuring the residual chlorine concentration after the application of the pretreatment voltage. For example, the reference number of times may be decreased as the measured value obtained by measuring the residual chlorine concentration increases (the residual chlorine concentration increases), and the reference number of times may be increased as the measured value obtained by measuring the residual chlorine concentration decreases (the residual chlorine concentration decreases). As a result, it is possible to determine the appropriate timing for applying the pretreatment voltage, taking into consideration that the easiness of adhesion of oxidation-reduction reaction products and the like to the electrode changes depending on the residual chlorine concentration.

Further, the residual chlorine meter of the second embodiment determines whether or not to apply the pretreatment voltage based on the number of measurements of the residual chlorine concentration after application of the pretreatment voltage. However, the present invention is not limited to this. Whether or not to apply the pretreatment voltage may be determined based on the elapsed time from the application of the pretreatment voltage. In this case, the microcontroller 14 determines whether or not the elapsed time from the application of the pretreatment voltage is equal to or longer than a predetermined reference time. When the elapsed time is equal to or longer than the reference time, the pretreatment voltage is applied before the measurement circuit 12 measures the residual chlorine concentration. As shown in FIG. 9B, when 21 days have passed since the application of the pretreatment voltage, the voltage between the working electrode and the reference electrode when immersed in the test solution is equal to or higher than the lower limits La, Lb, and Lc at which correct measurement results of the residual chlorine concentration can be obtained. Therefore, by setting the reference time to, for example, 21 days, it is possible to reduce the frequency of applying the pretreatment voltage while suppressing a decrease in the measurement accuracy of the residual chlorine concentration due to the adhesion of oxidation-reduction reaction products and the like to the working electrode.

Further, in such a residual chlorine meter, when determining whether or not to apply the pretreatment voltage based on the elapsed time after the application of the pretreatment voltage, the reference time that is the basis for the judgment may be changed based on the measured value obtained by actually measuring the residual chlorine concentration after the application of the pretreatment voltage. For example, the reference time may be shortened as the measured value obtained by measuring the residual chlorine concentration increases, and the reference time may be lengthened as the measured value obtained by measuring the residual chlorine concentration decreases. As a result, it is possible to determine the appropriate timing for applying the pretreatment voltage, taking into consideration that the easiness of adhesion of oxidation-reduction reaction products and the like to the electrode changes depending on the residual chlorine concentration.

Further, in the residual chlorine meter of the second embodiment, whether or not to apply the pretreatment voltage may be determined based on both the number of measurements of the residual chlorine concentration after the application of the pretreatment voltage and the elapsed time since the application of the pretreatment voltage. For example, the microcontroller 14 of the residual chlorine meter determines that the pretreatment voltage is to be applied when either the number of times the residual chlorine concentration is measured after the application of the pretreatment voltage is equal to or greater than the number reference value or the elapsed time is equal to or greater than a predetermined reference time. This makes it possible to determine the appropriate timing for applying the pretreatment voltage in consideration of the actual usage of the residual chlorine meter.

In addition, the present invention can be modified as appropriate within the scope not contrary to the gist or idea of the invention that can be read from the scope of claims and the entire specification, and the residual chlorine meter and residual chlorine concentration measuring method involving such modifications are also included in the technical concept of the present invention.

1 residual chlorine meter 2 working electrode (first electrode)
3 reference electrode (second electrode)
4 processing circuit 5 power supply circuit 11 pretreatment voltage application circuit (pretreatment section)
12 measurement circuit (measurement part)
13 switch 14 microcontroller (control unit)

Claims (6)

a first electrode that is a working electrode and a second electrode that is a reference electrode or a counter electrode are immersed in a test liquid, and a measurement unit that measures the residual chlorine concentration of the test liquid based on the voltage between the first electrode and the second electrode;
a pretreatment unit that applies a pretreatment voltage between the first electrode and the second electrode;
After applying the pretreatment voltage, the application of the pretreatment voltage is stopped, and then the residual chlorine concentration of the test solution is measured. A control unit that controls the measurement unit and the pretreatment unit,
The residual chlorine meter , wherein the pretreatment section sweeps the pretreatment voltage at a constant speed so that the waveform of the pretreatment voltage becomes a triangular wave . 2. The residual chlorine meter according to claim 1 , wherein the pretreatment section sweeps the pretreatment voltage around 0 V such that the amplitude on the plus side and the amplitude on the minus side are equal to each other. 3. The control unit determines whether or not the number of measurements of the residual chlorine concentration by the measuring unit after applying the pretreatment voltage is a predetermined number or more, and when the number of measurements is the predetermined number or more, the pretreatment voltage is applied before the next measurement of the residual chlorine concentration by the measurement unit, and when the number of measurements is less than the predetermined number, the control unit controls the pretreatment unit so that the pretreatment voltage is not applied before the next measurement of the residual chlorine concentration by the measurement unit. Residual chlorine meter described in. 4. The residual chlorine meter according to any one of claims 1 to 3 , wherein the control unit determines whether or not the elapsed time from the application of the pretreatment voltage is equal to or longer than a predetermined time, and controls the pretreatment unit so that when the elapsed time is equal to or longer than the predetermined time, the pretreatment voltage is applied before the residual chlorine concentration is measured by the measurement unit, and when the elapsed time is less than the predetermined time, the pretreatment voltage is not applied before the residual chlorine concentration is measured by the measurement unit. A first electrode that is a working electrode and a second electrode that is a reference electrode or a counter electrode are immersed in a test solution, and the residual chlorine concentration of the test solution is measured based on the voltage between the first electrode and the second electrode.
a pretreatment step of applying a pretreatment voltage between the first electrode and the second electrode;
a measuring step of measuring the residual chlorine concentration of the test solution based on the voltage between the first electrode and the second electrode after the application of the pretreatment voltage in the pretreatment step is stopped;
A residual chlorine concentration measuring method, wherein in the pretreatment step, the pretreatment voltage is swept at a constant speed so that the waveform of the pretreatment voltage is a triangular wave . 6. The residual chlorine concentration measuring method according to claim 5 , wherein, in said pretreatment step, said pretreatment voltage is swept around 0 V such that the amplitude on the plus side and the amplitude on the minus side are equal to each other.

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